Distractor

ABSTRACT

A distractor for osteogenesis, in particular in the front region of the lower or upper jaw, with first fixation means for fixation to a first, fixed bone fragment, and second fixation means for fixation to a second bone fragment, which is movable in relation to the first bone fragment in a defined plane, and also having an adjustment element connected to the first fixation means and to the second fixation means, and by the actuation of which the distance between the first fixation means and the second fixation means is variable, whereby the bone fragments to which the first fixation means and the second fixation means can be fixed can be moved away from or toward each other, wherein the first fixation means and the adjustment element are formed or connected to each other such that when the adjustment element is actuated, the second fixation means, which can be fixed to the movable bone fragment, can be pivoted out of the plane in which they can be fixed to the bone fragment.

FIELD OF INVENTION

The invention relates to a distractor for use with correcting trauma tothe mouth, face and jaw.

BACKGROUND

Distractors are used in osteosynthesis/osteogenesis, where they are usedin particular in the region of the mouth, jaw and face. A special fieldof application of such distractors lies in the front region of the jaw,for example the lower jaw (mandibula), or else in the front region ofthe upper jaw (maxilla). If, for example, the lower jawbone is atrophicin the front region, or if a segment of the lower jaw had to be cut awayon account of malignant neoplasms, or else after a lower jaw trauma, itis favorable for a reconstruction of the jaw with the aid of dentalimplants or prostheses if the alveolar ridge of the lower jaw in thefront region can first be reconstructed before the implants are set.

This typically takes place by the upper bone segment being mobilized(osteotomy, corticotomy) in the front region of the lower jaw—where thebone defect is to be rectified. With the aid of a distractor, themobilized bone segment is then raised slightly from the fixed lowerjawbone. The osteoinductive effect of the distraction causes new bone tobe formed between the raised bone segment and the fixed bone. Theraising of the movable bone segment is in this case performed in smallincrements, for as long as it takes for the alveolar ridge to bereconstructed. The gingiva (gum tissue) covering the osseous alveolarridge is likewise raised at the same time by the distraction.

Previously known distractors used in such applications typicallycomprise two bone plates (typically so-called miniplates), one of whichis fixed (for example by screwing) to the mobilized (by osteotomy,corticotomy) bone segment and the other of which is fixed to the fixedlower jawbone. An adjustment element (distraction spindle) is connectedto both bone plates. With the aid of the adjustment element, thedistance between the two bone plates can be varied. With appropriateactuation of the adjustment element, that bone plate which is fixed tothe mobilized bone segment is moved linearly along the spindle axis awayfrom that bone plate which is fixed to the fixed lower jawbone.

This tried-and-tested distraction procedure is in need of improvement,however, to the extent that the distraction only takes place strictly inthe direction of the spindle axis. Since, however, the lower jaw has acertain natural curvature—referring here not to the curvature of thelower jaw in the horizontal plane but to the curvature of the lower jaw(when viewed from the front) in the sagittal planes—this curvature ofthe lower jaw cannot be optimally replicated by the known distractors,because of the fact that the distraction can only take place strictly inthe direction of the spindle axis. Furthermore, the tensile force of thelabial frenulum also acts in the front region, so that it is especiallydifficult there for the alveolar ridge to be reconstructed as faithfullyas possible. However, it is specifically in the front region of thelower jaw (and also in the front region of the upper jaw) that the mostfaithful possible reconstruction of the alveolar ridge is particularlydesired.

SUMMARY

This is where the present invention comes in, the object of which is topropose a distractor with which it is intended to be possible inosteogenesis by means of distraction to permit the most optimum possibleshaping of the bone to be built up, and in particular in thereconstruction of an alveolar ridge of the lower or upper jaw to permitthe replication of the natural curvature of the jaw. The distractor ispreferably to be made in a form simply to produce.

This object is achieved by the distractor according to the invention asit is characterized by the features of the independent patent claim.Particularly advantageous refinements of the distractor according to theinvention emerge from the features of the dependent patent claims.

In particular, the distractor comprises first fixation means, forfixation to a first, fixed bone fragment, and second fixation means, forfixation to a second bone fragment, which is movable in relation to thefirst bone fragment, in a defined plane. The distractor also comprisesan adjustment element, which is connected to the first fixation means onthe one hand and to the second fixation means on the other hand, and bythe actuation of which the distance between the first fixation means andthe second fixation means is variable. This allows the bone fragments towhich the first and second fixation means can be fixed to be moved awayfrom or toward each other. The first fixation means and the adjustmentelement are formed or connected to each other in such a way that, whenthe adjustment element is actuated, the second fixation means, which canbe fixed to the movable bone fragment, can be pivoted out of the planein which they can be fixed to the bone fragment.

This pivotability of the second fixation means out of the plane in whichthey are fixed to the movable bone fragment allows the naturalconstruction of the alveolar ridge, for example of the lower jaw,because the direction in which the movable bone fragment (mobilized byosteotomy or corticotomy) is distracted in relation to the fixed(immobile) bone fragment can be changed during the buildup of the bone(osteogenesis) by distraction. This allows the natural curvature of thejaw to be taken into account and to be replicated as faithfully aspossible in the osteogenesis.

In the case of an exemplary embodiment of the distractor according tothe invention, the first fixation means comprise a first bone plate andthe second fixation means comprise a second bone plate, the adjustmentelement being connected to the first bone plate on the one hand and tothe second bone plate on the other hand. Fixation with the aid of boneplates (in particular with so-called miniplates) is a particularlyreliable method of fixation, which can also be mastered very well withrespect to the surgical procedures involved. However, fixation by othersuitable means (for example pins, etc.) could also be considered inprinciple, although fixation by means of bone plates is preferred.

The first bone plate may in this case be formed in such a way that ithas a longitudinal plate axis, the second bone plate being able to pivotabout this longitudinal plate axis or about an axis parallel to it. Asalready mentioned above—this pivotability of the second bone plate aboutthe longitudinal plate axis of the first bone plate or about an axisparallel to it allows the natural construction of the alveolar ridge,for example of the lower jaw, because the direction in which the movable(mobilized) bone fragment is distracted in relation to the fixed(immobile) bone fragment can be changed during the buildup of the bone(osteogenesis) by distraction. This allows the natural curvature of thejaw to be replicated as faithfully as possible in the osteogenesis.

In the case of an advantageous exemplary embodiment of the distractoraccording to the invention, the adjustment element is connected to thefirst fixation means or the first bone plate in the manner of a hinge.The hinge-like connection defines the pivot axis about which the secondfixation means or the second bone plate are or is pivotable.

In the case of an advantageous development of the distractor accordingto the invention, the hinge is formed as a film hinge. This type offormation of the hinge is particularly simple in terms of productionengineering.

In the case of a further advantageous development of the distractoraccording to the invention, a fixation element is provided which isconnected via the hinge to the first fixation means or the first boneplate and which has via the adjustment element a rigid connection to thesecond fixation means or the second bone plate. The adjustment elementcomprises a pivoting element for pivoting the second fixation means orthe second bone plate, which is connected to the fixation element on theone hand and to the first fixation means or the first bone plate on theother hand.

In this case, two or more thin webs, which form the hinge, may beprovided between the fixation element and the first fixation means orthe first bone plate. Two or more webs in this case prevent tilting ofthe fixation element and consequently tilting of the second fixationmeans or the second bone plate within their plane.

The fixation element and the hinge may be formed in one piece on thefirst fixation element or the first bone plate, which simplifiesproduction to the extent that the bone plate, the fixation element, andin the case of webs, also the webs can be produced in one and the sameproduction operation and do not have to be produced separately and thenconnected to one another in a suitable way.

In the case of a development of the distractor according to theinvention, the adjustment element comprises a distraction element forvarying the linear distance between the first and second fixation meansor the first and second bone plates, and also the pivoting element forpivoting the second bone plate, a rigid connection existing between thedistraction element and the pivoting element. A first retaining elementis fixed to the fixation element and a second retaining element is fixedto the first fixation means or the first bone plate. The pivotingelement has a threaded spindle and the first retaining element, which isfixed to the fixation element, has a through-bore with a thread forreceiving the threaded spindle. The threaded spindle is received in sucha way that it cannot be displaced in the direction of the spindle axisin the second retaining element, which is fixed to the first fixationmeans or to the first bone plate. This development represents a variantof the distractor according to the invention that is advantageous interms of constructional design and favorable in terms of production. Itis also advantageous to the extent that the “overall height” of thedistractor is maintained, and does not increase, during pivoting.

In the case of a further exemplary embodiment of the distractoraccording to the invention, the hinge is formed in such a way that thesecond fixation means or the second bone plate is pivotable in relationto the first fixation means or to the first bone plate by an absoluteangle of up to 30°, preferably of up to 15° (both pivoting directions).This range is large enough to replicate the natural curvatures inparticular in the jaw region.

The distractor according to the invention is preferably produced fromtitanium or some other biocompatible material, in order that it does notcause any reactions of the body.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantageous refinements of the distractor according to theinvention emerge from the description of an advantageous exemplaryembodiment which follows with the aid of the drawing, in which:

FIG. 1 shows an exemplary embodiment of a specific embodiment of adistractor according to the invention in a front view;

FIG. 2 shows the distractor from FIG. 1 in a rear view;

FIG. 3 shows the distractor from FIG. 1 in a perspective view from therear;

FIG. 4 shows the distractor from FIG. 1 in a perspective view from thefront (partly in section);

FIG. 5 shows the distractor from FIG. 1 in a side view in the neutralposition (partly in section);

FIGS. 6-8 show the distractor from FIG. 1 in three different pivotingpositions; and

FIGS. 9-11 show the distractor from FIG. 1 in three further pivotingpositions.

DETAILED DESCRIPTION

FIG. 1 shows a front view of an exemplary embodiment of a distractor 1according to the invention, as can be used in particular in the frontregion of the lower or upper jaw. The distractor 1 comprises a firstbone plate 3 and a second bone plate 2, which are in each casepreferably formed as an elongate miniplate. The second bone plate 2extends in the direction of its longitudinal plate axis 20. It has anumber of eyelets 21, through which bone screws (not represented) can bescrewed into the movable bone segment, in order to fix it to the movablebone segment. For this purpose, the plate holes 210 may be formed asthrough-holes; they may have a thread, which interacts with acorresponding screw thread, or they may have an engagement contourdiffering from a thread, for blocking the bone screw. Such an engagementcontour and the way in which it functions are described for example inWO-A-00/66012. Provided between the eyelets 21 of the bone plate 2 arewebs 22, which allow separation (cutting away) and/or bending of thebone plate 2 to the respective outer contour of the movable bonesegment.

The first bone plate 3 is likewise formed in an elongated manner andextends in the direction of its longitudinal plate axis 30. Inprinciple, the first bone plate 3 may also have the same shape as thesecond bone plate 2. The first bone plate 3 likewise has a number ofeyelets 31, provided in which are plate holes 310, which may in turn beformed as through-holes, may have a thread for interaction with acorresponding screw thread, or which may have an engagement contourdiffering from a thread, as described for example in the aforementionedWO-Ab 00/66012. Webs 32 are provided between the eyelets 31, so that thefirst bone plate can also be separated (cut away) and/or bent to thejawbone well (to be precise to a fixed bone segment of the jawbone).

The distractor 1 also comprises an adjustment element 4, which for itspart comprises a separate pivoting element 40 and a separate distractionelement 41. The pivoting element 40 and the distraction element 41 arerigidly connected to each other. Provided on the second bone plate 2 isa platelet 23 (see for example FIG. 2, FIG. 3), to which the distractionelement 41 (distraction spindle) is firmly connected, for examplewelded.

Provided on the first bone plate 3 is a fixation element, which here hasthe form of a platelet 33 (see for example FIG. 2, FIG. 3), which isconnected to the first bone plate 3 in the manner of a hinge. In thecase of the exemplary embodiment represented, the hinge is a film hinge,which here has two thin webs 51 and 52. Two such webs 51 and 52 areadvantageous to the extent that this very greatly hinders, if notprevents, tilting of the second bone plate 2 in the plane of the plate(here the plane of the paper). More than two webs may also be providedfor this purpose, but in principle a single web would also be sufficientto perform the hinge function (and could then be formed somewhat widerthan in the case of the two-web variant represented). The hinge couldalso be formed differently than a film hinge, as long as the hingefunction is ensured. With the aid of the hinge, here with the aid of thewebs 51 and 52, the second bone plate 2 in the exemplary embodimentshown is pivotable about an axis 300 parallel to the longitudinal plateaxis 30 of the first bone plate 3. That is to say that the second boneplate 2 in FIG. 1 can be pivoted out of the plane of the paper to thefront or to the rear about the axis 300, as explained more preciselyfurther below.

Provided on the fixation element—the platelet 33—is a first retainingelement 61 and provided on the first bone plate 3 is a second retainingelement 62, which can in each case be produced as separate parts andfixed to the platelet 33 or to the bone plate 3, for example by beingwelded on. Provided in the first retaining element 61 is a through-borewith a thread 610 (see FIG. 5), into which the thread of a threadedspindle 400 of the pivoting element 40 can engage. The second retainingelement 62 has a clearance 620 (FIG. 4, FIG. 5), in which the distal endof the threaded spindle 400 is received in such a way that it cannot bedisplaced in the direction of the spindle axis (see FIG. 1). On theother hand, the distal end of the threaded spindle 400 can otherwise bedisplaced very well within certain limits in the clearance 620,substantially to the front or rear, as will become evident further belowfrom the description of the way in which the distractor 1 functions.

The way in which the distractor 1 functions, in particular whenpivoting, is to be explained below on the basis of FIGS. 6-8 and FIGS.9-11. This explanation concentrates on the pivoting about the axis 300(see FIG. 1), that is the change of direction, while the lineardistraction—that is the change of the distance between the two boneplates—takes place in a known way by means of actuation of thedistraction element 41 (distraction spindle).

To understand the way in which the distractor functions during thepivoting, let us consider once again FIG. 5, in which the distractor 1is located in the neutral position (that is unpivoted). As a differencefrom this neutral position, the distractor in FIG. 6 is in a position inwhich the platelet 33 has been pivoted about an angle of, for example,α₁=5° in relation to its neutral position. This pivoting can be achievedby actuating the pivoting element 40, which may take place here with theaid of a suitable wrench (not represented), which acts on the polygonalhead 401 of the threaded spindle 400, so that the threaded spindle 400can be turned. When the polygonal,head 401 of the threaded spindleturns, the threaded spindle 400 attempts—by the interaction of thethread of the threaded spindle 400 with the thread 610 of the firstretaining element 61—to increase the distance do between the firstretaining element 61 and the second retaining element 62 in the axialdirection. In the neutral position, however, this is not possible in thedirection of extent of the spindle axis, because, as already describedabove, the distal end of the threaded spindle 400 is captured in theclearance 620 of the second retaining element 62 in such a way that itcannot be displaced in the axial direction. On the other hand, theturning of the threaded spindle 400 must cause the distance do whichexists between the first retaining element 61 and the second retainingelement 62 in the neutral position to be increased, otherwise thethreaded spindle 400 would not allow itself to be turned with a captureddistal end. Since, however, the webs 51 and 52 of the film hinge areflexible, the webs 51 and 52 are bent by the turning of the threadedspindle 400, and so the platelet 33 with the first retaining element 61fixed to it is pivoted about the axis of rotation 300 (see FIG. 1). As aresult, the distance d₀ between the two retaining elements 61 and 62 inthe neutral position (FIG. 5) is increased to the distance d₁ in theposition according to FIG. 6 (pivoting of the spindle axis by 50). Asthis takes place, the distal end of the threaded spindle slides slightlyoutward in the clearance 620 of the second retaining element 62.

With further turning of the threaded spindle 400, the platelet 33 withthe first retaining element 61 fixed to it comes into the position shownin FIG. 7, in which the platelet 33 has been pivoted about the angleα₂=10° with respect to the neutral position about the axis 300 (FIG. 1).The distance between the first retaining element 61 and the secondretaining element 62 in the direction of the spindle axis is therebyincreased to the distance d₂.

If the threaded spindle 400 is turned further, the platelet 33 with thefirst retaining element 61 fixed to it finally comes into the positionshown in FIG. 8, in which the platelet 33 has been pivoted by the angleα₃=15° with respect to the neutral position about the axis 300 (see FIG.1). The distance between the first retaining element 61 and the secondretaining element 62 in the direction of the spindle axis is therebyincreased to the distance d₃.

The pivoting of the platelet 33 in the other direction functions in-thesame way, as FIGS. 9-11 show in a simple way, the distance do (neutralposition according to FIG. 5) between the first retaining element 61 andthe second retaining element 62 initially being reduced there to thedistance d₄ with a pivoting angle α₄=5° of the platelet 33, whichdistance is reduced further to the distance d₅ with a pivoting angle ofα₅=10°, and which distance is finally reduced to the distance d₆ with apivoting angle of α₆=15°.

It is particularly advantageous in the case of the distractor 1according to the invention that the individual parts, that is the boneplates 2 and 3 together with the platelet 33 and the webs 51 and 52, aswell as the retaining elements 61 and 62, and also the pivoting element40 and the distraction element 41, can be produced separately in asimple and reliable way and can be joined together, for example by meansof welding, so that the distractor according to the invention can bemastered well in terms of production.

Titanium, which is known to be biocompatible, comes into considerationin particular as the material for the individual parts. Alternatively,other biocompatible materials may also be used, however, andbioresorbable materials may also be considered.

Specific embodiments of a Distractor according to the present inventionhave been described for the purpose of illustrating the manner in whichthe invention may be made and used. It should be understood thatimplementation of other variations and modifications of the inventionand its various aspects will be apparent to those skilled in the art,and that the invention is not limited by the specific embodimentsdescribed. It is therefore contemplated to cover by the presentinvention any and all modifications, variations, or equivalents thatfall within the true spirit and scope of the basic underlying principlesdisclosed and claimed herein.

1. A distractor for osteogenesis, in particular in the front region ofthe lower or upper jaw, with first fixation means for fixation to afirst, fixed bone fragment, and second fixation means for fixation to asecond bone fragment, which is movable in relation to the first bonefragment in a defined plane, and also having an adjustment elementconnected to the first fixation means and to the second fixation means,and by the actuation of which the distance between the first fixationmeans and the second fixation means is variable, whereby the bonefragments to which the first fixation means and the second fixationmeans can be fixed can be moved away from or toward each other, whereinthe first fixation means and the adjustment element are formed orconnected to each other such that when the adjustment element isactuated, the second fixation means, which can be fixed to the movablebone fragment, can be pivoted out of the plane in which they can befixed to the bone fragment.
 2. The distractor according to claim 1,wherein the first fixation means comprise a first bone plate and thesecond fixation means comprise a second bone plate, the adjustmentelement being connected to the first bone plate and to the second boneplate.
 3. The distractor according to claim 2, wherein the first boneplate has a longitudinal plate axis and the second bone plate can pivotabout the longitudinal plate axis or about an axis parallel to it. 4.The distractor according to claim 1 wherein the adjustment element isconnected to the first fixation means or to the first bone plate in themanner of a hinge.
 5. The distractor according to claim 4, wherein thehinge is formed as a film hinge.
 6. The distractor according to claim 4,including a fixation element connected via the hinge to the firstfixation means or to the first bone plate and which has via theadjustment element a rigid connection to the second fixation means orthe second bone plate, and wherein the adjustment element comprises apivoting element for pivoting the second fixation means or the secondbone plate, which is connected to the fixation element and to the firstfixation means or the first bone plate.
 7. The distractor according toclaim 6, further including two or more thin webs, which form the hinge,provided between the fixation element and the first fixation means orthe first bone plate.
 8. The distractor according to claim 6, whereinthe fixation element and the hinge are formed in one piece on the firstfixation means or the first bone plate.
 9. The distractor according toclaim 6, wherein the adjustment element comprises a distraction elementfor varying the linear distance between the first and second fixationmeans or the first and second bone plates as well as the pivotingelement for pivoting the second fixation means or the second bone plate,a rigid connection existing between the distraction element and thepivoting element and further including a first retaining element fixedto the fixation element and a second retaining element fixed to thefirst fixation means or the first bone plate, and wherein the pivotingelement has a threaded spindle and the first retaining element, which isfixed to the fixation element, has a through-bore with a thread forreceiving the threaded spindle, and wherein the threaded spindle isreceived such that it cannot be displaced in the direction of thespindle axis in the second retaining element, which is fixed to thefirst fixation means or the first bone plate.
 10. The distractoraccording to claim 4, wherein the hinge is formed such that the secondfixation means or the second bone plate is pivotable in relation to thefirst fixation means or to the first bone plate by an absolute angle ofup to 30°.
 11. The distractor according claim 1 formed from titanium orsome other biocompatible material.